Subnetting Guide: Learn How to Subnet with Examples and Diag

Subnetting Guide: A Practical Overview for Network Engineers

Introduction

Subnetting is one of the foundational concepts in networking, yet it often intimidates even experienced professionals. Whether you’re designing enterprise infrastructure or troubleshooting a misconfigured device, understanding how subnetting works is essential for managing IP address space efficiently.

In this guide, we’ll walk through what subnetting is, why it matters, how to calculate subnets, and where common mistakes occur. We’ll include clear examples, diagrams, and tables to help reinforce each concept. Finally, we’ll look at how noBGP changes the way we think about IP addressing and routing across distributed environments.

What is Subnetting?

Subnetting is the process of dividing a large IP network into smaller, more manageable segments called subnets. It allows for more efficient use of IP addresses and improves performance and security by isolating network traffic.

For example, instead of giving 254 devices access to the same /24 network, you might divide that network into multiple /26 subnets, isolating traffic into groups of 62 usable IPs.

Why Subnetting Matters

Subnetting serves several purposes:

• Efficient IP allocation: Avoid wasting large blocks of IPs on small networks.
• Improved performance: Reduces broadcast traffic and limits scope.
• Security: Isolates traffic between departments or zones.
• Scalability: Enables hierarchical network design for large environments.

Subnetting Basics: IP Addresses, Subnet Masks, and CIDR

An IP address has two parts:

• Network portion
• Host portion

The subnet mask (or CIDR notation) defines where that split happens.

How to Subnet a Network (Step-by-Step)

Let’s say you’ve been assigned the 192.168.10.0/24 network and need to create four subnets.

1. Determine needed bits
2. You need 4 subnets → 2² = 4 → take 2 bits from host portion
3. New CIDR
4. /24 + 2 bits = /26
5. Calculate subnet ranges
6. Each /26 has 64 addresses (62 usable):
   
   • 192.168.10.0 – 192.168.10.63
   • 192.168.10.64 – 192.168.10.127
   • 192.168.10.128 – 192.168.10.191
   • 192.168.10.192 – 192.168.10.255

Diagram: Subnetting a /24 Network

Each subnet has 64 total addresses: 1 network address, 1 broadcast, and 62 usable.

‍

Tools for Subnetting

If you don’t want to calculate manually every time, try:

• SubnetOnline
• ipcalc (Linux CLI)
• CIDR chart cheat sheets (great for exams and quick lookup)

Common Subnetting Pitfalls

1. Overlapping subnets
2. Two subnets shouldn’t share any IP space.
3. Not reserving enough hosts
4. Remember to account for future growth.
5. Broadcast domain confusion
6. Subnetting doesn’t eliminate broadcast traffic—it contains it.
7. Incorrect gateway assignment
8. Devices need the correct gateway within their subnet to reach outside.

Real-World Use Cases

• Corporate Networks
• Separate marketing, sales, and engineering into isolated subnets.
• Data Centers
• Assign subnets per rack or per VLAN.
• IoT and Edge Devices
• Use small subnets (/28 or /30) for low-traffic sensor networks.
• Cloud VPCs
• Define subnet ranges for public and private workloads.

Subnetting in Cloud and Multi-Cloud Environments

Subnetting gets more complicated when your infrastructure spans:

• Multiple cloud providers (AWS, GCP, Azure)
• Overlapping CIDRs across VPCs
• Third-party VPNs and NAT gateways

Cloud-native teams often run into CIDR collisions when connecting environments that were never intended to overlap.

How noBGP Changes the Game

Subnetting, while foundational, is also a manual, static process. In fast-paced, multi-cloud architectures, traditional subnetting becomes a source of:

• Network conflicts
• Hard-to-debug issues
• Cross-team coordination headaches

noBGP eliminates the need for manual subnetting between environments:

Key noBGP Benefits:

• No subnet collisions: You can connect overlapping CIDRs without conflicts.
• Service-level identity routing: Traffic isn’t bound to IP ranges.
• Instant VPC-to-VPC connections: Without complex subnet planning.
• Zero configuration of NAT, IPsec, or route tables

Instead of designing networks around IP addresses, noBGP lets you define who can talk to whom, regardless of subnet.

Summary: Traditional Subnetting vs. noBGP

‍

Final Thoughts

Subnetting is an essential skill for network engineers and sysadmins. It enables efficient IP space utilization, traffic isolation, and performance optimization. But it also introduces complexity, especially in modern, hybrid environments.

noBGP redefines the network boundary. Instead of designing around static IP ranges, you define secure, deterministic, and private connections based on identity—not infrastructure.

Ready to stop worrying about subnets?

Choose a network architecture built for how modern applications actually run.

‍

‍

‍

‍

‍

‍

‍

‍

‍